After the pilot has signalled the need for this service by going around, flying deadside at 600', waggling his wings, and squawking 7600 (if available).
On an
IFR flight?
without a positive clearance I would have gone around myself
What about the lost comms procedure for IFR?
Where do you draw the line?
I have never heard of the lost comms procedure terminating at a specific distance left to run
Some bigger airports do publish a specific procedure for lost comms, however.